Field
The present disclosure relates to a coupling device for coupling a rod to a bone anchoring element. The coupling device includes a receiving part for receiving a rod and for coupling the rod to a bone anchoring element. The receiving part is configured to accommodate a head of a bone anchoring element such that the head can pivot with respect to the receiving part. The coupling device further includes a pressure element with a flexible portion to clamp a head inserted therein and a clamping element configured to exert a compression force onto the pressure element to increase a friction force between the pressure element and the head.
Description of the Related Art
U.S. Pat. No. 8,926,671 describes a receiving part for receiving a rod and for coupling the rod to a bone anchoring element. The receiving part includes a receiving part body for accommodating a head of the bone anchoring element and a pressure element with a flexible portion to clamp an inserted head. The pressure element is movable along a longitudinal axis of the receiving part body from an insertion position where the head is insertable into the receiving part body to a pre-locking position where the head is clamped in the receiving part body by a pre-stress exerted by the pressure element. The pressure element is further movable to a locking position where the head is locked in the receiving part body. The pre-stress exerted by the pressure element allows a desired angular position of the bone anchoring element to be maintained relative to the receiving part by friction before the head of the bone anchoring element is finally locked.
U.S. Pat. No. 6,248,105 B1 describes a device for connecting a longitudinal rod with a bone anchoring element, such as a pedicle screw, thereby forming a fixation system for the spine. The device includes a connecting member accepting a longitudinal rod. A radially compressible spring chuck is arranged within the connecting member that has a cavity for receiving a head of the bone anchoring element. An insert slides into a bore hole of the connecting member and has a recess with a complementarily conical shape to a conical shape of the spring chuck. The insert radially compresses the spring chuck at an interface between the conical shapes and therewith fastens the head of the pedicle screw.
U.S. Pat. No. 8,951,294 B2 describes a spinal implant with an anchoring part and a mounting part with an internal axial housing to transversely receive a connecting rod. The spinal implant includes retaining elements that are situated near the bottom of the axial housing of the mounting part. The retaining elements are adapted to fasten a locking member in a stationary locking position in which a ball joint connection, formed by first and second connecting elements, is locked to fasten the anchoring part and the mounting part in rotation relative to each other about at least two orthogonal axes.
US 2013/0096622 A1 describes a polyaxial bone anchoring device having a pressure element that exerts pressure onto a head of an anchoring element. The pressure element maintains the head in an adjustable angular position relative to a receiving part by friction using threaded set screws. A desired friction force can be achieved by controlling the thread turning and advancement of the set screws.